Greenhouse and forced greenhouse climate control system and method

ABSTRACT

A greenhouse is disclosed that generally comprises an enclosed growing section with an enclosed end gable adjacent to the growing section. The end gable is arranged to flow air into the growing section. Air distribution tubes are included within the growing section with the tubes arranged to provide for substantially uniform air flow into the growing section. The air tubes can also be arranged to compensate for heat differential between the air in the tubes and in the growing section.

The present application is a continuation-in-part of and claims thebenefit of U.S. patent application Ser. No. 11/824,159 to Houweling,filed on Jun. 28, 2007, which claims the benefit of U.S. ProvisionalPatent Application No. 60/817,755, also to Houweling, filed on Jun. 29,2006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to greenhouses and more particularly to climatecontrol systems for greenhouses.

2. Background of the Invention

Greenhouses have been used for hundreds of years to grow differentvarieties of plants, including ornamental plants and fruit/vegetableproducing plants. Greenhouses typically comprise a structure with aplastic or glass roof and frequently glass or plastic walls. Theinterior of the greenhouse can be heated by incoming solar radiationthat warms the plants and soil therein. The closed environment of agreenhouse has its own unique requirements compared with outdoorproduction. Pests and diseases need to be controlled and irrigation isnecessary to provide water. Of equal importance, greenhouses can also bearranged to compensate for extreme highs and lows of heat and humidity,and to generally control the environmental conditions such as the levelof carbon dioxide (CO₂).

Different greenhouses have been developed to control the environmentalconditions in a greenhouse. U.S. Pat. No. 5,001,859 to Sprung describesa method and structure for environmental control of plant growth ingreenhouse conditions. The structure comprises a translucent stressedfabric shell on a base, with which to grow plants, the shell and basesealing the environment within the space against external environmentalconditions. The temperature and relative humidity within the productionareas are generally controlled by a microprocessor based series of spraysystems, along with a furnace. The spray systems can lower thetemperature in the space while at the same time increasing humidity, andthe furnace can be utilized to increase the temperature within thespace.

U.S. Pat. No. 5,813,168 to Clendening describes a greenhouse and amethod for controlling the environment of the interior space of thegreenhouse. The greenhouse includes an interior insulating panel and amovable exterior reflective panel capable of both insulating theinterior of the greenhouse and reflecting sunlight into the interior.The greenhouse also includes a closed-system heat exchanger having aplurality of spaced water-impermeable water flow passageways throughwhich water flows by gravitational forces and having a means for blowingair between the water flow passageways such that the air does notcontact the water and such that the air is either heated or cooled bythe water. In addition, the heat exchanger may include a water dischargeand/or a gas discharge for the control of humidity and gas levels withinthe greenhouse. Finally, the greenhouse includes hydroponic plant bedsdisposed on top of the heat exchangers and hydroponic solution tanksalong the outer interior walls of the greenhouse.

U.S. Pat. No. 5,212,903 to Talbot discloses a greenhouse for providingenvironmental control for growing plants comprising a frame defining astructure forming an interior region for holding plants. A flexiblecover is positioned over the frame for providing a roof enclosure forthe structure, and an elongate roller extends along the length of thestructure secured to a lengthwise edge of the cover. A power source iscoupled to the roller driving the roller about its longitudinal axis toretract or extend the cover relative to the frame. The greenhouse alsoincludes a water distribution system that includes a distributionconduit with spaced-apart spray nozzles positioned adjacent the topinterior of the greenhouse. A power drive system oscillates the conduitthrough a defined arc to distribute water downwardly to plants growingin the greenhouse. A timing means is associated with the power drive fordelaying the return rotation of the conduit to ensure that the outsideedges of the spray pattern will be watered evenly.

U.S. Pat. No. 7,228,657 to Brault et al. discloses a greenhouse havingan exterior curtain wall structure formed by spaced tubular postscarrying external transparent panels and bottom non-transparent wallpanels below a sill with the panels spanning the posts. A plurality ofelongate benches is located within the interior at spaced positionsalong one side wall with the width of the benches being equal to thepost spacing to form an expandable construction. Each bench hasassociated with it a respective air handling system for conditioningincluding a duct which is located partly under the respective bench anda fan in a fan housing at the side wall. From the fan a vertical ductsection extends to a flexible tube extending over the bench. Airdehumidification, fogging, heating and cooling are provided in the ductunder the bench. An alley is arranged along the opposite wall containingelectrical controls mounted in cabinets forming panels for mounting inthe span between posts.

European Patent Application No. EP 1 464 218 A1 discloses a method forgrowing crops arranged in a greenhouse that is closed off from theenvironment and wherein the climate is regulated and watering of thecrop is controlled within by a watering device. The photosynthesis andyield of the crop is regulated by controlling, independent of theoutside conditions, the CO₂ concentration in the greenhouse and thetranspiration by regulation of the temperature and air movements aroundthe crop. Air regulating means can be utilized such as partitions,screens and the like, and outlet openings for air at different heightsnear the crop are provided so that the climate near the crop, and inparticular the microclimate near the leaves of the crop, can beregulated and monitored.

International Application No. PCT/NL2000/000402 (Publication No. WO2000/076296) discloses a market garden greenhouse system in which plantproducts can be cultivated. The market greenhouse is closed in that itis substantially not provided with ventilating openings or ventilatingwindows that can be opened. The greenhouse comprises heat regulatingmeans for regulating heat therein, with heat generating from solarenergy and a heating system. The greenhouse can also comprise an airhumidity regulating means and surplus heat is removed from thegreenhouse to an aquifer in the summer.

SUMMARY OF THE INVENTION

One embodiment of a greenhouse according to the present inventioncomprises a growing section with an air or gas distribution systemwithin said growing section. The distribution system comprises one ormore conduits for distributing air or gas within the greenhouse withconduits carrying air or gas having different pressures along the lengthof the conduits. The conduits are arranged to provide substantiallyequal distribution of air or gas throughout the growing section.

One embodiment of a greenhouse air distribution system according to thepresent invention comprises a plurality of tubes to distribute airwithin a greenhouse. A system is included for providing a main air flowto the interior of at least one of the tubes, the air pressure withinthe tubes varying along its length. The tubes have holes to allow air toexit from the tubes with the holes formed to compensate for the pressurevariations to allow the tubes to provide for a substantially uniform airdistribution along their lengths.

Another embodiment of a greenhouse according to the present inventioncomprises an enclosed growing section with an enclosed end gableadjacent to the growing section. The end gable is arranged to flow airinto the growing section. Air distribution tubes are included within thegrowing section with the tubes arranged to provide for substantiallyuniform air flow into the growing section. The air tubes can also bearranged to compensate for heat differential between the air in thetubes and in the growing section.

These and other aspects and advantages of the invention will becomeapparent from the following detailed description and the accompanyingdrawings which illustrate by way of example the features of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view of one embodiment of a greenhouse andits climate control system according to the present invention;

FIG. 2 shows the greenhouse climate control system in FIG. 1 showinganother mode of air flow;

FIG. 3 is an end view of one embodiment of a greenhouse climate controlsystem according to the present invention;

FIG. 4 is a sectional view of one embodiment of a greenhouse climatecontrol system according to the present invention at the crop section ofthe greenhouse;

FIG. 5 is a side sectional view of another embodiment of a greenhouseclimate control system according to the present invention showing onemode of air-flow;

FIG. 6 shows the greenhouse climate control system in FIG. 1 showinganother mode of air flow;

FIG. 7 shows the louver and first vent feature of the greenhouse climatecontrol system in FIG. 5;

FIG. 8 is an end view of one embodiment of a greenhouse climate controlsystem according to the present invention;

FIG. 9 is side view of one embodiment of an air distribution tubeaccording to the present invention;

FIG. 10 is a sectional view of the tube in FIG. 9 taken along sectionlines 10-10;

FIG. 11 is side view of another embodiment of an air distribution tubeaccording to the present invention; and

FIG. 12 is a sectional view of the tube in FIG. 11 taken along sectionlines 12-12.

DETAILED DESCRIPTION OF THE INVENTION

The present invention generally relates to improved greenhouses andforced greenhouse climate control systems that are arranged to operatein different modes to control the temperature and environmentalconditions within the greenhouse. In one mode ambient air is drawn intothe greenhouse, and in other modes air from within the greenhouse isre-circulated. In still other modes, the system can draw ambient air incombination with recirculation of air, and when ambient air is drawn in,it can also be cooled. This arrangement provides for control of thegreenhouse climate using a simple and cost effective system.

In one embodiment of a greenhouse and greenhouse climate control systemaccording to the present invention, tubes are provided along the fulllength of the greenhouse growing section. Ambient and or re-circulatedair is drawn into the tubes and each of the tubes has a means forallowing air to exit along its length, such as through holes along thelength of the tubes. The number and size of holes is arranged to promoteeven distribution of air from the tubes throughout the greenhousestructure. It is understood that other devices can be used beyond tubesfor flowing air into the greenhouse, and different means for allowingair to exit from the tubes can be used. The separation (spacing) betweenthe tubes can vary and the diameter of the tubes can vary depending onthe particular circumstances including but not limited to thesurrounding climate, or crops being grown. In different embodiments thetubes can also be above the greenhouse crop or below gutters tables orother systems in the greenhouse.

Fans or other mechanisms for drawing air are arranged on the tubes tosupply a flow of air volume to the tubes to cool the greenhouse duringthe expected elevated outside (external) temperatures and to heat thegreenhouse during expected low temperatures. In one embodiment, arespective one of fans is located at one end of each of the tubes andflows air into and along the length of the tubes. It is understood,however, that the fans can be located in other positions on the tubesand a single fan can be used to flow air into more than one of thetubes.

The climate control system according to the present invention is alsoarranged to efficiently flow air of different temperatures into thetubes to control the temperature in the greenhouse during temperaturecycles of the surrounding climate. When the temperature within thegreenhouse rises, cooler gases are provided to the greenhouse tubes, andin one embodiment the cooler air is provided from the ambient airoutside the greenhouse. Systems can also be used to further cool theambient air as it enters the greenhouse, if necessary. When thetemperature in the greenhouse is at or near the desired level air fromwithin the greenhouse can be circulated into the tubes. When thetemperature within the greenhouse falls, known internal heater systemscan be used to heat the air in the greenhouse with the heated airre-circulated to the tubes. To achieve the desired temperature withinthe greenhouse a controller can be employed to automatically provide forthe different modes above or provide a combination of the modes. Thesystems according to the present invention can also control the pressurewithin the greenhouse and the level of certain gases such as carbondioxide (CO₂).

Conventional greenhouse air distribution systems can distribute unequalamounts of gas along the length of the greenhouse. In the case of tubesprovided along the length of the greenhouse, equally spaced perforationsare provided along the tube to allow air or gas to pass from within thetube to the interior of the greenhouse. The air or gas is typicallysupplied to the tube from one end, and as a result of pressuredifferences and turbulence along the length of the tube, an unequaldistribution of air can exit from the tube at different points along itslength.

Another problem that may be encountered is a temperature difference overthe length of the tube due to radiation and convection from or into theair tube, resulting in unequal temperatures. While still otherchallenges in providing homogeneous air distribution can result from airexiting the tube at an angle corresponding to the direction of airflowthrough the tube. In areas of turbulence, the air can emit at differentdirections from the holes, contributing to non-homogeneous airdistribution along the tube.

As further described below, these problems can be minimized oreliminated by utilizing an air distribution system arranged according tothe present invention. The distribution systems can be arranged todistribute equal amounts of air of a substantial homogeneous quality ofthe entire length of the greenhouse. In some embodiments the distancebetween perforations can be varied along the length to compensate forthe pressure differences and turbulence. In other embodiments, the tubescan be arranged with compartments along its length that provide abarrier between the main flow in the tube and air exiting from the tube.This not only reduces the effects of the turbulence, but also providesand insulation barrier to reduce unequal temperatures along the lengthof the tube.

The present invention is described herein with reference to certainembodiments but it is understood that the invention can be embodied inmany different ways and should not be construed as limited to theembodiments set forth herein. In particular, the present invention isdescribed below in regards to greenhouse features arranged in aparticular way but it is understood that these features can be arrangedin different ways and can be used in other applications.

It is also understood that when an element or feature is referred to asbeing “on” or “adjacent” another element or feature, it can be directlyon or adjacent the other element or feature or intervening elements orfeatures may also be present. Furthermore, relative terms such as“outer”, “above”, “lower”, “below”, and similar terms, may be usedherein to describe a relationship of one feature to another. It isunderstood that these terms are intended to encompass differentorientations in addition to the orientation depicted in the figures.

Although the terms first, second, etc. may be used herein to describevarious elements or components, these elements or components should notbe limited by these terms. These terms are only used to distinguish oneelement or component from another element or component. Thus, a firstelement or component discussed below could be termed a second element orcomponent without departing from the teachings of the present invention.

Embodiments of the invention are described herein with reference todifferent views and illustrations that are schematic illustrations ofidealized embodiments of the invention. As such, variations from theshapes of the illustrations as a result, for example, of manufacturingtechniques and/or tolerances are expected. Embodiments of the inventionshould not be construed as limited to the particular shapes of theregions illustrated herein but are to include deviations in shapes thatresult, for example, from manufacturing.

FIGS. 1-4 show one embodiment of greenhouse 10 utilizing a forcedgreenhouse climate control system 12 according to the present invention.The greenhouse 10 has a gabled end 14 that is separated from the cropgrowing section 16 of the greenhouse by partition 22. The majority ofthe climate control system 12 is housed within the gabled end 14 with aportion of the system continuing into the crop growing section 16. Thecrop section 16 comprises a portion of the system comprising devices fordistributing air from the gabled end 14 throughout the crop growingsection 16. Many different distribution devices can be used, with asuitable device being a plurality of tubes 18 running the length of thecrop section. As mentioned above, different numbers of tubes can be usedwith greenhouse 10 shown having five (5) tubes 18. The tubes 18 openthrough the partition 22 such that air from the gabled end 14 can flowinto the tubes 18 and pass into the growing end through tube holes.Different numbers and sizes of holes can be included along the length ofthe tubes 18 to insure even distribution.

Fans 20 can be placed on or close to the bottom of the partition 22between the gabled end 14 and the section 16 each at a respective one ofthe tubes 18. The fans 20 are arranged to pull or flow air into itsrespective one of the tubes 18 from in the gabled end 14. The air in thegabled end 14 can include ambient air from outside the greenhouse 10 orair from inside the crop section 16 during recirculation, or combinationof the two. As more fully described below, this is accomplished by alouver and vent system within the greenhouse 10.

The greenhouse 10 further comprises a first vent/opening 24 (“firstvent”) in the outside gable wall 26 through which ambient air can enterthe gabled end 14. The first vent 24 can be arranged in many differentlocations, with a suitable location as shown being on the lower portionof the outside gable wall. In the embodiment shown, one first vent 24 isshown, but it is understood that more than one vent can be included. Thefirst vent 24 can be arranged in many different ways, with the preferredvent running substantially the length of the outside gable wall 26.

A cooling mechanism 28 can be included at the first vent 24 to cool airbeing pulled into the gabled end 14, and/or to control the humiditywithin the air. In one embodiment the cooling mechanism 28 is aconventional pad cooling system that is known in the art and notdescribed in detail herein. A screen can also be included over the vent24 to prevent insects and other pests from entering the greenhouse 10.

In some embodiments, a heat exchanger 28 can be included at or near thefans 20 to further heat or cool the air passing into the tubes 18. Heatexchangers are generally known in the art and the basic operation isonly briefly discussed herein. According to the present invention, thegreenhouse 10 can be arranged to store heated water from the heatexchanger for use in heating the greenhouse at a later time.

The heat exchanger 29 relies on a flow of water to cool air passingthrough the fan 20 as it enters the tube 18. The cooling of the air bythe water passing though the heat exchanger can result in the warming ofthe water flowing through the heat exchanger. In some embodiments, thiswarmed water can be stored in a separate storage tank for later use inwarming the air in the crop section 16. For example, warm water can fillthe storage tank when the temperature of the air is high, such as duringthe day. The warmed water can be stored and at night, when thetemperature dips, the warm water can be flowed into the heat exchanger29 to warm the air passing into the tubes.

A first louver 30 can be included at the outside gable wall 26 that ismovable in the directions of arrow 31 to control the amount of airentering the end gable 14. When operating in the mode to block air fromentering the end gable 14 the louver is lowered to cover the first vent24. When operating in the mode to allow air to enter the end gable 14,the louver 30 can be raised so that it is not blocking air from enteringor can be partially raised such that it is partially blocking air fromentering. As shown, the first louver 30 can be a planar shield that canslide down to fully or partially cover the first vent 24 depending onthe desired amount of air to pass through the vent 24. It is understoodthat many different mechanisms can be used beyond the first louver 30described above and the second louver described below.

The partition 22 comprises a second vent 34 that is located near the topof the partition 22, although the vent 34 can be in many differentlocations. A second louver 36 can be included at the partition 22 thatoperates similar to the first louver 30. The second louver 36 can bemoved in the direction of arrow 37 to block air from entering throughthe second vent 34, or can be moved so that it is not blocking air fromentering or is partially blocking air from entering. Like the firstlouver, the second louver 36 can be a planar shield that can slide downto fully or partially cover the second vent 34 depending on the desiredamount of air to pass through the vent 34.

The crop section 16 of the greenhouse 10 can also comprise one or moreconventional greenhouse vents (not shown) to allow excess air to bereleased from the greenhouse 10. This is particularly useful whenambient air is being drawn into the greenhouse. The release of airthrough the vents releases excess air that can build up in the cropsection 16. These vents are generally known in the art and are notdescribed herein. It is understood that these vents can also includescreens to prevent insects from entering and the vents are preferablylocated at or near the greenhouse roof. In some embodiments, the ventscan include fans to assist in the release of air, and it is understoodthat air can be released from the greenhouse using many differentmechanisms beyond conventional vents.

In operation, when the air temperature within the crop section 16 risesit may be desirable to pull cooler air into the section 16. This isreferred to as the cooling mode and is illustrated by the first airflow38 shown in FIG. 1. The second louver 36 can be closed and the firstlouver 30 can be at least partially opened to allow air to pass throughthe first vent 24. Fans 20 can be activated to pull greenhouse ambientair through the first vent 24 and in those embodiments where additionalcooling of the air is desired, the cooling mechanism 28 can be activatedto cool the air pulled through the vent 24. The cooled air enters thegabled end 14 and is pulled into the tubes 18 by the fans 20. The cooledair is then distributed evenly throughout the crop section 16 throughthe holes in the tubes 18. The heat exchanger 28 can also contain a flowof water to further cool water entering the tubes 18. As additionalambient air is pulled into the greenhouse, excess air can be releasedfrom the greenhouse through roof vents.

When the air within the greenhouse is at the desired temperature orneeds to be increased, the greenhouse enters the recycle mode as shownby second airflow 40 is FIG. 2. The first louver 30 can be closed andthe second louver 36 opened. The fans 20 can then be activated to pullair from within the greenhouse section 16 into the gabled end 14. Theair is then pulled into the tubes 18 and the air is distributedthroughout the greenhouse through holes in the tubes 18. Thiscirculation can continue as the temperature is maintained at its desiredlevel. If the air needs to be heated, known heating systems can beemployed within the greenhouse with one such system supplying heatedwater to rails or pipes in the greenhouse floor. Alternatively, heatedwater can be supplied to the heat exchanger 29 from the supply of heatedwater as described above. Air heated by this system can then becirculated until the desired temperature is achieved within thegreenhouse 10. Alternatively, the growing section can rely on the heatgenerated from sunlight passing into the growing section through thetransparent roof or sidewalls.

As mentioned above, the system 12 can also be operated to supply acombination of air to the tubes 18 from a combination of airflows 38 and40. This can be accomplished by controlling the opening of the first andsecond louvers 30 and 36 while the fans 20 are operating. The fans 20,first and second louvers 30, 36 and the heat exchanger 29, arepreferably operated under computer control using various known sensorsand hardware/software combinations.

The greenhouse 10 and its forced greenhouse climate control system 12provide for improved and cost effective control of the greenhouseclimate compared to conventional systems. It is particularly useful indesert climates where it is useful to provide cost effective systems forminimizing the maximum heat experienced by crops within a greenhouse.For example, one embodiment of the greenhouse 10 can reduce what wouldtypically be 33° C. temperature in greenhouse to 26° C. withoutemploying expensive cooling systems. This reduction in temperature canhave a dramatic impact on the improved health and growth of crops withinthe greenhouse.

FIGS. 5-8 show another embodiment of greenhouse 50 that is similar tothe greenhouse 10 described above and shown in FIGS. 1-4. The greenhouse50 also utilizing a forced greenhouse climate control system 52according to the present invention. The greenhouse 50 has a gabled end54 that is separated from the crop holding section 56 of the greenhouse50 by partition 62. The crop section 56 comprises an air distributingdevice to distribute air from the gabled end 54 throughout the cropsection 56. Many different distribution devices can be used, with asuitable device being a plurality of tubes 58 running the length of thecrop section 56 similar to the tubes 18 in greenhouse 10. As mentionedabove, different numbers of tubes can be used with greenhouse 10 shownhaving ten (10) tubes 58 as best shown in FIG. 10. Referring again toFIGS. 5 and 6 the tubes 58 open through the partition 62 such that airfrom the gabled end 54 can flow into the tubes 58.

Fans 60 can placed in or close to the partition 62 between. Each of thetubes 58 are connected to an opening in the partition lower portion ofthe partition 62. A respective fan 60 is then arranged over each of theopenings and air from each of the fans 60 flows into its respective oneof the tubes 58. The fans 60 are arranged with the ability to pullambient air from in the gabled end into the tubes during operation. Thiscan either be ambient air or re-circulated air, or combination of thetwo.

The greenhouse 50 further comprises a vent/opening (“vent”) in theoutside gable wall 66 through which ambient air can enter the gabled end54. The vent 64 is similar to the opening 24 in greenhouse 10 describedabove but is located near the center of the gabled wall 66, as shown.The vent 64 preferably runs the length of the gabled wall and althoughone vent 64 is shown it is understood that more than one opening can beincluded.

A cooling mechanism 68 can also be included at the vent 64 to cool airbeing pulled in into the gabled end 54, and/or to control the humiditywithin the air. In one embodiment the cooling mechanism 68 is aconventional pad cooling system that also runs the length of and isincluded over the vent 64. A screen 69 can also be included over thevent 64 to prevent insects and other pests from entering the greenhouse50. A heat exchanger 68 can also be included at or near the fans 60 thatis arranged and operates similar to the heat exchanger 29 shown in FIGS.1 and 2 and described above. The heat exchanger 68 can further heat orcool air entering the tubes 58 as described above.

A first louver 70 can be included inside of gable wall 66 that ismovable in the directions of arrows 73 to control the amount of ambientair entering the end gable 54. When operating in the mode to block airfrom entering the end gable 54 the louver 70 is closed to cover the vent64. When operating in the mode to allow air to enter the end gable 54,the louver 70 can be swing open so that it is not blocking air fromentering or can be partially opened such that it is partially blockingair from entering. As the louver 70 swings from its closed and fullyblocking position over the first vent/opening 64 it also blocksre-circulating air that would otherwise be pulled into the tubes 58 bythe fans 60. The greenhouse further comprises a shelf 71 on the insidesurface of the partition 62. When the louver 70 is fully opened itslower surface abuts the shelf 71 to fully block re-circulating air frombeing drawn by the fans 60. Instead, in this position the fans 60 drawprimarily ambient air that can be cooled by cooling mechanism 68. It isunderstood that many different mechanisms can be used beyond the firstlouver 70 described above.

The partition 62 comprises a second vent/opening 74 that is located nearthe top of the partition 62, although the vent 74 can be in manydifferent locations. Unlike the vent 34 described above in greenhouse10, the vent 74 does not have a second louver and remains open throughoperation. The amount of air from the crop section 56 drawn through bythe fans and re-circulated into the tubes is controlled by the extent towhich the louver 70 is opened. If the louver 70 is fully closed all ofthe air drawn through the fans 60 comes through vent 74 forre-circulating. When the louver 70 is fully open no air through the ventis drawn by the fans. When the louver is at different positions betweenfully open and closed, the fans draw a combination of ambient and airthrough the vent 74.

The crop section 56 can also comprise one or more conventionalgreenhouse vents (not shown) to allow excess air to be released from thegreenhouse 50. These vents are generally known in the art and are notdescribed herein. The greenhouse vents are preferably located at or nearthe greenhouse roof and can include fans to assist in the release ofair. It is understood that air can be released from the greenhouse usingmany different mechanisms beyond conventional vents.

The greenhouse 50 operates similar to the greenhouse 10. In operation,when the air temperature within the crop section 56 rises it may bedesirable to pull cooler air into the section 56. This is referred to asthe cooling mode and is illustrated by the first airflow 78 shown inFIG. 5. The louver 70 can be at least partially opened to allow ambientair to pass through the first vent 64. Fans 60 can be activated to pullambient air through the vent 64 and in those embodiments whereadditional cooling of the air is desired, the cooling mechanism 68 canbe activated to cool the air pulled through the vent 64. The cooled airenters the gabled end 54 and is pulled into the tubes 58 by the fans 60.The cooled air can be further cooled by heat exchanger 67 and the cooledair is then distributed evenly throughout the crop section 56 throughthe holes in the tubes 58. As additional ambient air is pulled into thegreenhouse, excess air can be released from the greenhouse through roofvents.

When the air within the greenhouse is at the desired temperature thegreenhouse enters the recycle mode as shown by second airflow 80 in FIG.6. The first louver 70 can be closed and the fans 60 can then beactivated to pull air from within the greenhouse section 56 into thegabled end through the second vent 74. This circulation can continue asthe temperature is maintained at its desired level. If the air needs tobe heated, known heating systems can be employed within the greenhousewith one such system supplying heated water to rails in the greenhousefloor as described above. Alternatively, warm water can be supplied tothe heat exchanger 68 from the separate heated water supply as describedabove with reference to heat exchanger 29. As ambient or recycled airpasses through the fans 60 it is heated and passed into tubes 58. As theheated air exits the tubes it heats the air within the crop section. Airheated by this system can then be circulated until the desiredtemperature is achieved within the greenhouse 50.

As mentioned above, the system 12 can also be operated to supply acombination of air to the tubes 18 from a combination of airflows 78 and80. This can be accomplished by controlling the opening of the louver 70while the fans 60 are operating. Like the embodiment above, the fans 60,louver 70, heat exchanger 67 are preferably operated under computercontrol using various known sensors and hardware/software combinations.

It is understood that there are many additional advantages andalternative arrangements provided by the present invention. Oneadvantage is that the crop section can be over-pressurized by the system52, which can prevent undesired insects. The invention further providesfor enhanced crop yields by allowing for greater levels of radiation toreach the plants by eliminating conventional roof vent superstructuresand accompanying insect netting. The crop section 56 can also bearranged so that a gas, such as CO₂ can be fed into and more efficientlymaintained within the section 56. The gas feed systems are known in theart and not discussed in detail herein. These gases can further enhancethe health and growth of the crop within section 56.

In alternative embodiments, the fans 60 can be controlled and operatedas variable drive fans to provide additional control over airflow. Thevents can be different sizes and more vents can be included in manydifferent locations.

In still other embodiments, the greenhouse can be arranged without agabled end. For example, the first louver can be arranged over the fanswith the cooling mechanism located at the fans such that ambient air canbe pulled directly into the tubes with the air passing the coolingmechanism for additional cooling. Pipes can be included and arranged toprovide an air passageway between the second vent and the fans duringthe mode when air from within the crop section is to be recycled. Thisis only one of the many alternative arrangements for greenhouses andforced greenhouse climate control systems according to presentinvention.

As discussed above, one air distribution according to the presentinvention can comprise tubes running the length of the crop section ofthe greenhouse. It is understood, however, that the present inventioncan also comprise any other mechanism that can distribute air in acontrolled fashion, including but not limited to different types ofconduits. As mentioned above, in greenhouse 10 different numbers oftubes 18 and different numbers and sizes of holes can be included alongthe length of the tubes to provide even distribution. FIGS. 9 and 10show one embodiment of an air distribution tube 100 according to thepresent invention comprising an outer tube 102 and an inner tube 104.The inner and outer tubes 104, 102 can be made of many differentmaterials such as known polymer materials.

Outer tube holes 106 are provided in the outer tube 102, and inner tubeholes 108 are included in the inner tube 104. By changing the pattern ofthe outer tube holes 106, the inner tube holes 108, or both, differentamounts of air are allowed to pass out of the tube 102 at differentlocations along the tube 102. In different embodiments the pattern ofholes can vary in different ways along the length of the tube 102 tocompensate for pressure variations, with the appropriate pattern can bedetermined during design of the air distribution system and greenhousearrangement.

In one embodiment according to the present invention, the first outertube section 110 can have holes 110 a that are further apart compared toother tube sections, with section 110 corresponding to a tube sectionwith higher pressure passing through it. By having holes further apart,less air passes from the tube in section 110, allowing for a more equaldistribution of air along all the sections of the tube. The holes can bechanged in other ways to compensate for different pressures along thetube. The second outer tube section 112 can also have second tube holes112 a that are larger than the holes in other sections. Second tubesection 112 can correspond to a tube section with lower pressure, withthe larger holes allowing more air out in those sections, to equalizethe air exiting along the outer tube 102. Different size and spacingarrangements can be provided along the length of the tube, and althoughthe holes are shown in outer tube 102 as being in straight line, it isunderstood that the holes can be provided in many different arrangementssuch as staggered, wavy, zigzag, random, etc. The changes in the holesize and arrangement are shown in outer tube 102, but it is understoodthat the holes can also be varied in the inner tube 104, or in both theouter tube 102 and inner tube 104.

For tube 100, the inner tube 104 can have a smaller diameter than theouter tube 102, at least along some sections of the tube. In theembodiment shown the outer tube 102 has a diameter that varies slightlyalong its length between a diameter that is the same as the inner tube104 and a diameter that is slightly larger than the inner tube 104. Insome embodiments where the inner tube 104 and outer tube 102 have thesame diameter, the two can be bonded together, although in otherembodiments the two may not bonded together. In still other embodimentsthe inner tube 104 can have a diameter that varies within the other tubeto form the compartments. In all these embodiments, compartments 114 areformed between the inner tube 102 and the outer tube 104, and in theembodiment shown, multiple compartments 114 are formed along the lengthof the tube 100. It is understood, however, that other embodiments canhave larger or smaller compartments and can also be arranged with asingle compartment along the length of the tube 100, between the innertube 104 and outer tube 102.

The compartments 114 encourage air exiting the tube 100 without beinginfluenced by the direction of the main air flow or turbulence withinthe tube 100. As best shown in FIG. 10, the main air flow from the innertube 102 passes through the inner tube holes 108 into the compartments114. The inner tube holes 104 are offset from the outer tube holes 102such that much of the turbulence or directional nature of the air flowis dissipated in the compartments 114 before exiting from the tube 100through outer tube holes 106. This allows the air to exit the tube in adirection that is substantially perpendicular to the tube 100. Thisallows for controlled dissipation of air from the tube 100 so that itenters the greenhouse at the desired location.

In some applications it may also be desirable to reduce the effects ofthe temperature difference between the man air flow within the tube 100and the temperature of the air within the greenhouse. The compartments114 along with the offset of the outer holes 106 and inner holes 108 andcompartments 114, provides for a double walled buffer zone that acts asan insulating barrier between the main air flow and the greenhouse. Thisarrangement of compartments 114 concentrates heat loss in air flowwithin the double walled buffer zone before the air is blown into thegreenhouse environment. This helps equalize the temperature of the airentering the greenhouse from the tube 100, even with a substantialdifference in temperature between the main air flow and the greenhouse.

The inner and outer tube arrangement of tube 100 also provides theadvantage of having no barriers or restrictions in the inner tube 104 toequalize pressure along the tube 100. This results in an airdistribution system that can consumes less energy in distributing aircompared to systems having tubes with restrictions.

FIGS. 11 and 12 show another embodiment of an air distribution tube 200according to the present invention, also having an outer tube 202 and aninner tube 204 that can be arranged similar to those in tube 100described above. The tube also comprises outer tube holes 206 and innertube holes 208 that can have varying distances between adjacent holesand can have different sizes as discussed above to compensate fordifferent air pressures and turbulence within the main air flow of thetube 200. The tube 200 can also have compartments 214 that also allowair to exit the tube 200 without being influenced by the direction ofthe main air flow within the tube 200. The compartment can also bearranged to reduce the effects of the temperature difference between theman air flow within the tube 200 and the temperature of the air withinthe greenhouse as described above.

As mentioned above, the outer tube holes 206 and inner tube holes 208can have many different offsets, with the offsets in tube 200 beingdifferent from those in tube 100. The inner tube holes 208 are equallyspaced around the circumference of the inner tube 204 and the outer tubeholes 206 arranged on opposite sides of the outer tube 202. It isunderstood that the holes in the inner and outer tubes can be offset inmany different ways beyond those shown in tube 100 and 200.

Although the present invention has been described in detail withreference to certain preferred configurations thereof, other versionsare possible. Therefore, the spirit and scope of the invention shouldnot be limited to the versions described above.

1. A greenhouse, comprising: a growing section; a air or gasdistribution system within said growing section, said distributionsystem comprising one or more conduits for distributing air or gaswithin said greenhouse, said conduits carrying air or gas havingdifferent pressures along their length and said conduits arranged toprovide substantially equal distribution of air or gas throughout saidgrowing section.
 2. The greenhouse of claim 1, wherein said conduitshave interior compartments.
 3. The greenhouse of claim 1, wherein saidconduits comprises one or more air distribution tubes within saidgrowing section, with a main airflow entering said growing section fromsaid climate control system passing into said tubes, said tubes havingholes to distribute said main air flow within said tubes to said growingsection in substantially equal distribution.
 4. The greenhouse of claim3, wherein said tubes are arranged to reduce directional forcesexperienced by air distributed in said growing section from said mainair flow in said tubes.
 5. The greenhouse of claim 3, wherein said tubesare arranged to reduce the temperature differential between said mainair flow and said growing section.
 6. The greenhouse of claim 3, whereinthe amount of air exiting said tube varies along the length of said tubeto compensate for turbulence or pressure differences with said tube. 7.The greenhouse of claim 3, wherein the distance between holes along saidtube is varied to compensate for turbulence or pressure differenceswithin said tube.
 8. The greenhouse of claim 3, wherein the size of saidholes is varied along said tube to compensate for turbulence or pressuredifferences within said tube.
 9. The greenhouse of claim 1, wherein saidconduits comprise one or more air distribution tubes having an innertube within an outer tube.
 10. The greenhouse of claim 9, wherein saidinner tube comprises inner tube holes to allow air to pass from withinsaid inner tube, and said outer tube has outer tube holes that allow forair from passing from said inner tube to pass into said growing section.11. The greenhouse of claim 9, comprising a compartment between saidinner and outer tubes.
 12. The greenhouse of claim 9, comprising aplurality of compartments between said inner and outer tubes.
 13. Thegreenhouse of claim 9, comprising a plurality of compartments betweensaid inner and outer tubes to reduce directional forces on air exitingsaid tubes.
 14. The greenhouse of claim 9, wherein said compartmentsreduce the temperature differential between said main air flow and saidgrowing section.
 15. The greenhouse of claim 10, wherein said inner tubeholes are offset from said outer tube holes
 16. A greenhouse airdistribution system, comprising: a plurality of tubes to distribute airwithin a greenhouse; a system for providing a main air flow to theinterior of at least one of said tubes, the air pressure within saidtubes varying along its length, wherein said tubes having holes to allowair to exit from said tubes, said holes formed to compensate for saidpressure variations to allow said tubes to provide for a substantiallyuniform air distribution along their lengths.
 17. The greenhouse ofclaim 16, wherein said tube have interior compartments.
 18. The systemof claim 16, wherein the pattern or size of said tube holes can vary tocompensate for said pressure variations.
 19. The system of claim 16,wherein said tubes are arranged to reduce directional forces experiencedby air distributed in said greenhouse from said air flow in said tubes.20. The system of claim 16, wherein said tubes are arranged to reducethe temperature differential between said main air flow and saidgreenhouse.
 21. The system of claim 16, wherein said tubes comprise aninner tube within an outer tube.
 22. The system of claim 21, whereinsaid inner tube comprises inner tube holes to allow air to pass fromwithin said inner tube, and said outer tube has outer tube holes thatallow for air from passing from said inner tube to pass into saidgreenhouse.
 23. The system of claim 21, comprising a plurality ofcompartments between said inner and outer tubes.
 24. The system of claim21, comprising a plurality of compartments between said inner and outertubes.
 25. The system of claim 21, wherein said inner tube holes areoffset from said outer tube holes.
 26. A greenhouse, comprising: anenclosed growing section; an enclosed end gable adjacent to said growingsection, said end gable arranged to flow air into said growing section;and air distribution tubes within said growing section, said tubesarranged to provide for substantially uniform air distribution into saidgrowing section and compensating for the heat differential between saidair in said tubes and in said growing section.
 27. The greenhouse ofclaim 26, comprising compartments within said tubes arranged to allowair from within said tube to pass into said compartment, and to passfrom said compartments into said growing section.